Migrator: Add a 'Report a problem' button

Fixes #41485

Change-Id: If5c4347ad177b7050a90a4549a880f49577ada8f
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/144522
Commit-Queue: Samuel Rawlins <srawlins@google.com>
Reviewed-by: Mike Fairhurst <mfairhurst@google.com>

41458.dart

@@ -0,0 +1,9 @@
+class A {}
+
+extension AList on Iterable<A> {
+  get foo => null;
+}
+
+extension AMap on Map<String, A> {
+  get bar => values.foo; // <-- foo is underlined red
+}

pkg/analysis_server/lib/src/edit/nnbd_migration/resources/index.html

@@ -65,6 +65,7 @@
         migration help</a>
     <span class="wide"> </span>
     <div>Based on {{ sdkVersion }}</div>
+    <button class="report-problem">Report a Problem</button>
 </footer>
 </body>
 </html>

pkg/analysis_server/lib/src/edit/nnbd_migration/resources/migration.css

@@ -65,6 +65,11 @@ header .apply-migration, .rerun-migration {
   margin: 10px;
 }
 
+footer .report-problem {
+  right: 0px;
+  margin: 4px 8px;
+}
+
 .rerun-migration .required {
   display: none;
 }
@@ -113,7 +118,7 @@ footer {
   display: flex;
   flex-direction: row;
   align-items: center;
-  padding: 8px 24px;
+  padding: 8px 0 8px 24px;
 }
 
 footer .wide {

pkg/analysis_server/lib/src/edit/nnbd_migration/web/migration.dart

@@ -62,6 +62,12 @@ void main() {
         document.body.classes.remove('rerunning');
       }
     });
+
+    final reportProblemButton = document.querySelector('.report-problem');
+    reportProblemButton.onClick.listen((_) {
+      window.open('https://goo.gle/dart-null-safety-migration-tool-issue',
+          'report-problem');
+    });
   });
 
   window.addEventListener('popstate', (event) {